Any variable speed fan drive using a variable diameter sheave and a movable motor base must have positive stops or limit switches to prevent movement of the base beyond the maximum and minimum speed positions. The fan speed is automatically adjusted by a combination of movement of the motor and changing the effective diameter of the variable sheave mounted on the motor shaft. Such automatic adjustments are conventional. To replace the variable speed belt, it is necessary to move the base of the motor past the high speed limit switch controlled position so that the belt can be easily slipped off and on the pulley. Conventionally, the high speed limit switch or stop would be removed or repositioned in an operation requiring tools and the motor base would then be moved to the desired position to permit replacement of the belt. In such a case, after the new belt is installed and the motor is repositioned, there is a possibility that the high limit switch or stop would either not be repositioned or would be incorrectly repositioned which could result in the failure of the device.